How to install the new version 12 of FreeNAS, installation principles for a beginner?

Question

FreeNAS

I'm not a Linux pro and have little experience with FreeNAS 11.3, so the question might be. silly: To upgrade to the latest version of FreeNAS and create a boot disk, do I have to rufus create an installation disk / flash drive with version 12, and then install everything from the beginning (in mode 1)? Or do I need to start in update mode (2) because I have a working version of 11.3 and disks with information. I need to save the disks - there is information! Where can you read about it? And is it possible, having kept the previous bootloader-flash drive (11.3) and played enough with version 12 and in case of bugs with it, return to 11.3 by simply booting from the old flash drive?

Answer 1

Make and save a separate backup of the config. Update in-place or make a separate flash drive with the new system. Please note! that in version 12 it is no longer recommended to use a USB flash drive as a system disk. If the data disks are not reformatted and the zpool is not updated, then nothing should happen to the data. But still, before such operations it is recommended to make a backup.
upd:
You can play / test on a virtual machine, why do it on a combat system? You can also plan/test the update process there.